<bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Background:</b> An organization's internal communication is an important factor shaping employees’ organizational commitment. Internal communication practices can be classified into three types according to the direction of information flow: top-down, bottom-up, and horizontal communication. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Research questions:</b> 1. What are the relationships between the three types of internal communication and organizational commitment? 2. Are there any mediating routes that bridge the relationship between internal communication and organizational commitment? 3. Do the effects of internal communication on organizational commitment vary for different jobs? <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Literature review:</b> Based on the social exchange theory, we uncover the underlying mechanism of the relationships between the three types of internal communication and organizational commitment. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Methodology:</b> A structural equation model using partial least squares was employed to analyze survey data from 12,817 full-time employees in the Chinese internet sector. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Results and conclusions:</b> The results suggest that top-down, bottom-up, and horizontal communication affect organizational commitment positively and significantly via the mediating routes of employees’ perceived job attractiveness or perceived customer service performance. The study also reveals a fit between employees’ job characteristics (e.g., information-processing demands) and internal communication types to improve organizational commitment. These findings generate theoretical and practical implications for professional communication management.